This invention relates to the field of intracorporeal medical devices such as guidewires for advancing intraluminal devices including stent delivery catheters, balloon dilatation catheters, atherectomy catheters and other intraluminal devices within a patient""s body lumen.
Conventional guidewires for angioplasty, stent delivery, atherectomy and other vascular procedures usually comprise an elongated core member with one or more tapered sections near the distal end thereof and a flexible body such as a helical coil or a tubular body of polymeric material disposed about the distal portion of the core member. The flexible body may extend proximally to an intermediate portion of the guidewire. A shapable member, which may be the distal extremity of the core member or a separate shaping ribbon which is secured to the distal extremity of the core member extends through the flexible body and is secured to the distal end of the flexible body by soldering, brazing or welding which forms a rounded distal tip. Torquing means are provided on the proximal end of the core member to rotate, and thereby steer, the guidewire while it is being advanced through a patient""s vascular system.
Further details of guidewires, and devices associated therewith for various interventional procedures can be found in U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.): U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams et al.); and U.S. Pat. No. 5,345,945 (Hodgson, et al.) which are hereby incorporated herein in their entirety by reference thereto.
In a typical coronary procedure using a guidewire, a guiding catheter having a preformed distal tip is percutaneously introduced into a patient""s peripheral artery, e.g. femoral or brachial artery, by means of a conventional Seldinger technique and advanced and steered therein until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery.
There are two basic techniques for advancing a guidewire into the desired location within a patient""s coronary anatomy through the in-place guiding catheter. The first is a preload technique which is used primarily for over-the-wire (OTW) catheters and the second is the bare wire technique which is used primarily for rail type catheters.
With the preload technique, a guidewire is positioned within an inner lumen of an OTW device such as a dilatation catheter or stent delivery catheter with the distal tip of the guidewire just proximal to the distal tip of the catheter and then both are advanced through the guiding catheter to the distal end thereof. The guidewire is first advanced out of the distal end of the guiding catheter into the patient""s coronary vasculature until the distal end of the guidewire crosses the arterial location where the interventional procedure is to be performed, e.g. a lesion to be dilated or an arterial region where a stent is to be deployed. The catheter, which is slidably mounted onto the guidewire, is advanced out of the guiding catheter into the patient""s coronary anatomy over the previously introduced guidewire until the operative portion of the intravascular device, e.g. the balloon of a dilatation or a stent delivery catheter, is properly positioned across the arterial location. Once the catheter is in position with the operative means located within the desired arterial location, the interventional procedure is performed. The catheter can then be removed from the patient over the guidewire. Usually, the guidewire is left in place for a period of time after the dilatation or stent delivery procedure is completed to ensure reaccess to the distal arterial location if it is necessary. For example, in the event of arterial blockage due to dissected lining collapse, a rapid exchange type perfusion balloon catheter such as described and claimed in U.S. Pat. No. 5,516,336 (McInnes et al), can be advanced over the in-place guidewire so that the balloon can be inflated to open up the arterial passageway and allow blood to perfuse through the distal section of the catheter to a distal location until the dissection is reattached to the arterial wall by natural healing.
With the bare wire technique, the guidewire is first advanced by itself through the guiding catheter until the distal tip of the guidewire extends beyond the arterial location where the procedure is to be performed. Then a rail type catheter, such as described in U.S. Pat. No. 5,061,273 (Yock) and the previously discussed McInnes et al. patent, which are incorporated herein by reference, is mounted onto the proximal portion of the guidewire which extends out of the proximal end of the guiding catheter and which is outside of the patient. The catheter is advanced over the guidewire, while the position of the guidewire is fixed, until the operative means on the rail type catheter is disposed within the arterial location where the procedure is to be performed. After the procedure the intravascular device may be withdrawn from the patient over the guidewire or the guidewire advanced further within the coronary anatomy for an additional procedure.
An important attribute for guidewires is having sufficient radiopacity to be visualized under a fluoroscope, allowing the surgeon to advance the guidewire to a desired intraluminal location, particularly the distal extremity of the guidewire. Unfortunately, the most suitable materials for guidewires, such as stainless steel and NiTi alloys, exhibit relatively low radiopacity. Accordingly, various strategies have been employed to overcome this deficiency. Portions of the guidewire, usually the shapeable distal tip, are typically made from or coated with highly radiopaque metals such as platinum, iridium, gold or alloys thereof. For example, a 3 to 30 cm platinum tip coil is frequently soldered to the distal extremity of the guidewire. An obvious drawback of these prior art methods is the high expense and scarcity of highly radiopaque metals and the difficulty and expense of manufacturing products from these materials. The requirement of both a high degree of radiopacity, high strength and flexibility can present design problems.
Accordingly, there remains a need for guidewires having sufficient radiopacity to allow visualization under a fluoroscope without the extensive use of expensive radiopaque metals such as platinum, gold, iridium and the like.
The present invention is directed to an intracorporeal device such as a guidewire having an elongate core member with a proximal core section and a distal core section and a flexible body such as a helical coil formed of metallic wire which is disposed about and secured to at least a portion of the distal core section.
In accordance with the invention, the intracorporeal product has a body with multi-components, at least one highly radiopaque component and at least one high strength component having less radiopacity than the highly radiopaque component. The amount of the highly radiopaque component and the high strength component of the flexible body depends upon the radiopacity of each of the components. Generally, however, the highly radiopaque component should be at least about 10% but not be more than about 60%, preferably about 20% to about 40%, of the total transverse cross-section of the flexible body. The greater radiopacity the high strength component has, lessens the amount of the expensive highly radiopaque material which is needed.
The highly radiopaque material of the coil may be selected from the group of platinum, gold, iridium, highly radiopaque alloys thereof. The presently preferred highly radiopaque material is an alloy of 90%(wt) Pl and 10%(wt.) Ir. The high strength material of the coil may be selected from the groups consisting of radiopaque materials such as tantalum, tungsten and silver and non-radiopaque materials such as stainless steel, NiTi alloys and Coxe2x80x94Crxe2x80x94Mo alloys. Tantalum and alloys thereof are preferred because these materials have significant radiopacity in addition to being high strength and can more significantly reduce the amount of expensive radiopaque material which much be used for a particular degree of radiopacity. For example, a solid wire of 90% platinumxe2x80x9410% iridium will provide complete radiopacity, whereas, a wire of the same thickness with 70% tantalum core and 30% of a 90% Ptxe2x80x9410% Ir alloy cladding will provided the same degree of radiopacity but substantially improved mechanical properties. The use of non-radiopaque high strength metals will provide a fair radiopacity with adequate or improved mechanical properties depending upon the material used. A thickness of about 5 to about 10 micrometers of highly radiopaque material will usually provide complete radiopacity for intracorporeal use with conventional fluoroscopic observation.
The presently preferred form of the flexible body which is secured to the distal core section is a two component metallic wire member such as a helical coil. Other forms include a multi-wire braid formed of two-component metallic wires. In one presently preferred embodiment, the two-component wire is made of a highly radiopaque cladding and a relatively high strength material. In this way, the radiopaque material of the cladding can be chosen for its radiopaque properties and the core material can be chosen for strength properties that enhance the guidewire""s performance. Alternatively, the core material may be highly radiopaque and the cladding may be formed of the high strength material.
The distal end of the helical coil may attached directly or indirectly to the distal end of the core member and it may also be secured to the core member at one or more proximal locations.
In order to increase the flexibility of the distal section of the guidewire, the core member of the guidewire may be formed in a conventional manner with a distal section having at least one tapered segment, wherein the elongate core member tapers distally to reduced transverse dimensions. If desired, the one or more distally tapered segments of the distal section of the elongate core member may be marked with radiopaque markers to indicate where a tapered segment begins or ends. In this way, a physician using the guidewire is able to identify the relative flexibility and stiffness of an area of interest on the guidewire using fluoroscopic imaging.
A second or proximal coil formed of helically shaped wire may be provided proximal to the radiopaque first coil which is formed of less radiopaque material. The wire forming the second coil may have a circular transverse cross-section or a substantially rectangular cross section. A coil of wire having a rectangular cross section provides increased stiffness and coil integrity as compared to wire with a round cross section of similar thickness, due to the increased cross sectional area. The proximal end of the second coil is attached to the distal section of the elongate core member by means of adhesive, solder and the like. The distal end of the second coil is preferably secured to the distal section of the core member by the same mass of solder or the like that secures the proximal end of the first, highly radiopaque coil to the core member.
The flexible body of the present invention has at least adequate radiopacity and strength while being substantially cheaper to make than similar structures with helical coils formed of precious metal such as platinum and gold. By appropriately choosing the materials, properties can be obtained which are better than conventional products, while significantly reducing costs.
These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings.